This invention relates to air control systems for internal combustion engines and more particularly to a method of diagnosing degradation in an air assisted injector system of an engine having electronic throttle control.
Internal combustion engines use fuel injectors to precisely control the amount of fuel inducted into the engine""s cylinders. Also, fuel injectors atomize the liquid fuel, increasing the homogeneity of the air and fuel mixture. Air assisted injectors provide auxiliary airflow to the engine which bypasses the throttle. Air assisted injectors use this airflow to enhance fuel atomization. Air assisted injectors are preferred in vehicles where additional fuel atomization can promote better combustion and lower regulated emissions. Air assisted injector systems can influence vehicle emissions, however, and therefore are subject to governmental regulations. These regulations require, among other things, that the air assisted injector systems be monitored for malfunctions.
Emissions diagnostics can be conducted during different engine operating states, such as acceleration, deceleration, fuel shutoff, or steady state idle. In automotive applications, a primary concern of any diagnostic test is that it be transparent to the vehicle operator. For robustness and accuracy of the diagnostic, however, it may be necessary to alter the flow of air or fuel to the engine.
Accordingly, there is a need for a diagnostic procedure which detects degradations in the air assisted injector system, yet is transparent to the vehicle operator.
It is an object of the present invention to provide an air assisted injector diagnostic which accurately detects faults in an air assisted injector of an internal combustion engine having electronic throttle control while the engine is operating at steady state idle.
The above object is achieved by providing a method of diagnosing faults in an air assisted fuel injector system of an internal combustion engine having electronic throttle control. The method comprises the steps of measuring the airflow entering an intake of the electronic throttle of the engine at idle speed with the air assisted injector system operating at a first rate of airflow, turning the air assisted injector system off, measuring the airflow entering the intake of the electronic throttle of the engine at idle speed with the air assisted injector system off, and generating an error signal as a function of the two measured values. This error signal can be used, for example, to alert the operator of an emission system malfunction.
Other objects and advantages of the present invention will become apparent upon considering the following detailed description and appended claims, and upon reference to the accompanying drawings.